Curated Optogenetic Publication Database

Search precisely and efficiently by using the advantage of the hand-assigned publication tags that allow you to search for papers involving a specific trait, e.g. a particular optogenetic switch or a host organism.

Showing 1 - 25 of 64 results

Optogenetic control of integrin-matrix interaction.

red PhyB/PIF6 HEK293T HeLa MCF7 Signaling cascade control Control of cell-cell / cell-material interactions
Commun Biol, 8 Jan 2019 DOI: 10.1038/s42003-018-0264-7 Link to full text
Abstract: Optogenetic approaches have gathered momentum in precisely modulating and interrogating cellular signalling and gene expression. The use of optogenetics on the outer cell surface to interrogate how cells receive stimuli from their environment, however, has so far not reached its full potential. Here we demonstrate the development of an optogenetically regulated membrane receptor-ligand pair exemplified by the optically responsive interaction of an integrin receptor with the extracellular matrix. The system is based on an integrin engineered with a phytochrome-interacting factor domain (OptoIntegrin) and a red light-switchable phytochrome B-functionalized matrix (OptoMatrix). This optogenetic receptor-ligand pair enables light-inducible and -reversible cell-matrix interaction, as well as the controlled activation of downstream mechanosensory signalling pathways. Pioneering the application of optogenetic switches in the extracellular environment of cells, this OptoMatrix–OptoIntegrin system may serve as a blueprint for rendering matrix–receptor interactions amendable to precise control with light.

Optogenetic Delineation of Receptor Tyrosine Kinase Subcircuits in PC12 Cell Differentiation.

blue VfAU1-LOV PC-12 Signaling cascade control Cell differentiation
Cell Chem Biol, 27 Dec 2018 DOI: 10.1016/j.chembiol.2018.11.004 Link to full text
Abstract: Nerve growth factor elicits signaling outcomes by interacting with both its high-affinity receptor, TrkA, and its low-affinity receptor, p75NTR. Although these two receptors can regulate distinct cellular outcomes, they both activate the extracellular-signal-regulated kinase pathway upon nerve growth factor stimulation. To delineate TrkA subcircuits in PC12 cell differentiation, we developed an optogenetic system whereby light was used to specifically activate TrkA signaling in the absence of nerve growth factor. By using tyrosine mutants of the optogenetic TrkA in combination with pathway-specific pharmacological inhibition, we find that Y490 and Y785 each contributes to PC12 cell differentiation through the extracellular-signal-regulated kinase pathway in an additive manner. Optogenetic activation of TrkA eliminates the confounding effect of p75NTR and other potential off-target effects of the ligand. This approach can be generalized for the mechanistic study of other receptor-mediated signaling pathways.

Development of a Wireless-Controlled LED Array for the Tunable Optogenetic Control of Cellular Activities.

blue CRY2/CIB1 HeLa Signaling cascade control Control of vesicular transport
Engineering, 6 Dec 2018 DOI: 10.1016/j.eng.2018.08.005 Link to full text
Abstract: Prohibitins (PHBs) are a highly conserved class of proteins first discovered as inhibitors of cellular proliferation. Since then PHBs have been found to have a significant role in transcription, nuclear signaling, mitochondrial structural integrity, cell division, and cellular membrane metabolism, placing these proteins among the key regulators of pathologies such as cancer, neuromuscular degeneration, and other metabolic diseases. The human genome encodes two PHB proteins, prohibitin 1 (PHB1) and prohibitin 2 (PHB2), which function not only as a heterodimeric complex, but also independently. While many previous reviews have focused on the better characterized prohibitin, PHB1, this review focuses on PHB2 and new data concerning its cellular functions both in complex with PHB1 and independent of PHB1.

Membrane dynamics induced by a PIP3 optogenetic tool.

blue CRY2/CIB1 Cos-7 HEK293 NIH/3T3 Signaling cascade control Control of cytoskeleton / cell motility / cell shape
Anal Sci, 2 Nov 2018 DOI: 10.2116/analsci.18sdp06 Link to full text
Abstract: Membrane dynamic structures such as filopodia, lamellipodia, and ruffles have important cellular functions in phagocytosis and cell motility, and in pathological states such as cancer metastasis. Phosphatidylinositol 3,4,5-trisphosphate (PIP3) is a crucial lipid that regulates PIP3 dynamics. Investigations of how PIP3 is involved in these functions have mainly relied on pharmacological interventions, and therefore have not generated detailed spatiotemporal information of membrane dynamics upon PIP3 production. In the present study, we applied an optogenetic approach using the CRY2–CIBN system. Using this system, we revealed that local PIP3 generation induced directional cell motility and membrane ruffles in COS7 cells. Furthermore, combined with structured illumination microscopy (SIM), membrane dynamics were investigated with high spatial resolution. We observed PIP3-induced apical ruffles and unique actin fiber behavior in that a single actin fiber protruded from the plasma membrane was taken up into the plasma membrane without depolymerization. This system has the potential to investigate other high-level cell motility and dynamic behaviors such as cancer cell invasion and wound healing with high spatiotemporal resolution, and could provide new insights of biological sciences for membrane dynamics.

Real-Time Genetic Compensation Defines the Dynamic Demands of Feedback Control.

blue CRY2/CIB1 S. cerevisiae Signaling cascade control
Cell, 18 Oct 2018 DOI: 10.1016/j.cell.2018.09.044 Link to full text
Abstract: Biological signaling networks use feedback control to dynamically adjust their operation in real time. Traditional static genetic methods such as gene knockouts or rescue experiments can often identify the existence of feedback interactions but are unable to determine what feedback dynamics are required. Here, we implement a new strategy, closed-loop optogenetic compensation (CLOC), to address this problem. Using a custom-built hardware and software infrastructure, CLOC monitors, in real time, the output of a pathway deleted for a feedback regulator. A minimal model uses these measurements to calculate and deliver-on the fly-an optogenetically enabled transcriptional input designed to compensate for the effects of the feedback deletion. Application of CLOC to the yeast pheromone response pathway revealed surprisingly distinct dynamic requirements for three well-studied feedback regulators. CLOC, a marriage of control theory and traditional genetics, presents a broadly applicable methodology for defining the dynamic function of biological feedback regulators.

RalB directly triggers invasion downstream Ras by mobilizing the Wave complex.

blue CRY2/CIB1 HEK293T Signaling cascade control Control of cytoskeleton / cell motility / cell shape
Elife, 15 Oct 2018 DOI: 10.7554/elife.40474 Link to full text
Abstract: The two Ral GTPases, RalA and RalB, have crucial roles downstream Ras oncoproteins in human cancers; in particular, RalB is involved in invasion and metastasis. However, therapies targeting Ral signalling are not available yet. By a novel optogenetic approach, we found that light-controlled activation of Ral at plasma-membrane promotes the recruitment of the Wave Regulatory Complex (WRC) via its effector exocyst, with consequent induction of protrusions and invasion. We show that active Ras signals to RalB via two RalGEFs (Guanine nucleotide Exchange Factors), RGL1 and RGL2, to foster invasiveness; RalB contribution appears to be more important than that of MAPK and PI3K pathways. Moreover, on the clinical side, we uncovered a potential role of RalB in human breast cancers by determining that RalB expression at protein level increases in a manner consistent with progression toward metastasis. This work highlights the Ras-RGL1/2-RalB-exocyst-WRC axis as appealing target for novel anti-cancer strategies.

Light-based tuning of ligand half-life supports kinetic proofreading model of T cell activation.

blue LOVTRAP Jurkat Signaling cascade control
bioRxiv, 4 Oct 2018 DOI: 10.1101/432864 Link to full text
Abstract: T cells are thought to discriminate stimulatory versus non-stimulatory ligands by converting small changes in ligand binding half-life to large changes in cell activation. Such a kinetic proofreading model has been difficult to test directly, as existing methods of altering ligand binding half-life also change other potentially important biophysical parameters, most notably the stability of the receptor-ligand interaction under load. Here we develop an optogenetic approach to specifically tune the binding half-life of a light-responsive ligand to a chimeric antigen receptor without changing other binding parameters. By simultaneously manipulating binding half-life while controlling for receptor occupancy, we find that signaling is strongly gated by ligand binding half-life. Our results provide direct evidence of kinetic proofreading in ligand discrimination by T cells.

Optogenetic control shows that kinetic proofreading regulates the activity of the T cell receptor.

red PhyB/PIF6 Jurkat Signaling cascade control Immediate control of second messengers
bioRxiv, 1 Oct 2018 DOI: 10.1101/432740 Link to full text
Abstract: The pivotal task of the immune system is to distinguish between self and foreign antigens. The kinetic proofreading model (KPR) proposes that T cells discriminate self from foreign ligands by the different ligand binding half-lives to the T cell receptor (TCR). It is challenging to test KPR as the available experimental systems fall short of only altering the binding half-lives and keeping other parameters of the ligand-TCR interaction unchanged. We engineered an optogenetic system using the plant photoreceptor phytochrome B to selectively control the dynamics of ligand binding to the TCR by light. Combining experiments with mathematical modeling we find that the ligand-TCR interaction half-life is the decisive factor for activating downstream TCR signaling, substantiating the KPR hypothesis.

Optogenetic control of epithelial-mesenchymal transition in cancer cells.

blue CRY2/CIB1 A549 HeLa Signaling cascade control Control of cytoskeleton / cell motility / cell shape Cell differentiation
Sci Rep, 20 Sep 2018 DOI: 10.1038/s41598-018-32539-3 Link to full text
Abstract: Epithelial-mesenchymal transition (EMT) is one of the most important mechanisms in the initiation and promotion of cancer cell metastasis. The phosphoinositide 3-kinase (PI3K) signaling pathway has been demonstrated to be involved in TGF-β induced EMT, but the complicated TGF-β signaling network makes it challenging to dissect the important role of PI3K on regulation of EMT process. Here, we applied optogenetic controlled PI3K module (named 'Opto-PI3K'), which based on CRY2 and the N-terminal of CIB1 (CIBN), to rapidly and reversibly control the endogenous PI3K activity in cancer cells with light. By precisely modulating the kinetics of PI3K activation, we found that E-cadherin is an important downstream target of PI3K signaling. Compared with TGF-β treatment, Opto-PI3K had more potent effect in down-regulation of E-cadherin expression, which was demonstrated to be regulated in a light dose-dependent manner. Surprisingly, sustained PI3K activation induced partial EMT state in A549 cells that is highly reversible. Furthermore, we demonstrated that Opto-PI3K only partially mimicked TGF-β effects on promotion of cell migration in vitro. These results reveal the importance of PI3K signaling in TGF-β induced EMT, suggesting other TGF-β regulated signaling pathways are necessary for the full and irreversible promotion of EMT in cancer cells. In addition, our study implicates the great promise of optogenetics in cancer research for mapping input-output relationships in oncogenic pathways.

Cancer mutations and targeted drugs can disrupt dynamic signal encoding by the Ras-Erk pathway.

red PhyB/PIF6 16HBE14o- BEAS-2B HCC827 II-18 NCI-H1395 NCI-H441 NIH/3T3 Signaling cascade control Cell cycle control
Science, 31 Aug 2018 DOI: 10.1126/science.aao3048 Link to full text
Abstract: The Ras-Erk (extracellular signal-regulated kinase) pathway encodes information in its dynamics; the duration and frequency of Erk activity can specify distinct cell fates. To enable dynamic encoding, temporal information must be accurately transmitted from the plasma membrane to the nucleus. We used optogenetic profiling to show that both oncogenic B-Raf mutations and B-Raf inhibitors can cause corruption of this transmission, so that short pulses of input Ras activity are distorted into abnormally long Erk outputs. These changes can reshape downstream transcription and cell fates, resulting in improper decisions to proliferate. These findings illustrate how altered dynamic signal transmission properties, and not just constitutively increased signaling, can contribute to cell proliferation and perhaps cancer, and how optogenetic profiling can dissect mechanisms of signaling dysfunction in disease.

Optical activation of TrkA signaling.

blue CRY2/CIB1 CRY2/CRY2 NIH/3T3 PC-12 Signaling cascade control Cell differentiation
ACS Synth Biol, 5 Jul 2018 DOI: 10.1021/acssynbio.8b00126 Link to full text
Abstract: Nerve growth factor/tropomyosin receptor kinase A (NGF/TrkA) signaling plays a key role in neuronal development, function, survival, and growth. The pathway is implicated in neurodegenerative disorders including Alzheimer's disease, chronic pain, inflammation, and cancer. NGF binds the extracellular domain of TrkA, leading to the activation of the receptor's intracellular kinase domain. TrkA signaling is highly dynamic, thus mechanistic studies would benefit from a tool with high spatial and temporal resolution. Here we present the design and evaluation of four strategies for light-inducible activation of TrkA in the absence of NGF. Our strategies involve the light-sensitive protein Arabidopsis cryptochrome 2 (CRY2) and its binding partner CIB1. We demonstrate successful recapitulation of native NGF/TrkA functions by optical induction of plasma membrane recruitment and homo-interaction of the intracellular domain of TrkA. This approach activates PI3K/AKT and Raf/ERK signaling pathways, promotes neurite growth in PC12 cells, and supports the survival of dorsal root ganglion neurons in the absence of NGF. This ability to activate TrkA using light bestows high spatial and temporal resolution for investigating NGF/TrkA signaling.

Four Key Steps Control Glycolytic Flux in Mammalian Cells.

red PhyB/PIF6 NIH/3T3 Signaling cascade control
Cell Syst, 26 Jun 2018 DOI: 10.1016/j.cels.2018.06.003 Link to full text
Abstract: Altered glycolysis is a hallmark of diseases including diabetes and cancer. Despite intensive study of the contributions of individual glycolytic enzymes, systems-level analyses of flux control through glycolysis remain limited. Here, we overexpress in two mammalian cell lines the individual enzymes catalyzing each of the 12 steps linking extracellular glucose to excreted lactate, and find substantial flux control at four steps: glucose import, hexokinase, phosphofructokinase, and lactate export (and not at any steps of lower glycolysis). The four flux-controlling steps are specifically upregulated by the Ras oncogene: optogenetic Ras activation rapidly induces the transcription of isozymes catalyzing these four steps and enhances glycolysis. At least one isozyme catalyzing each of these four steps is consistently elevated in human tumors. Thus, in the studied contexts, flux control in glycolysis is concentrated in four key enzymatic steps. Upregulation of these steps in tumors likely underlies the Warburg effect.

A platform of BRET-FRET hybrid biosensors for optogenetics, chemical screening, and in vivo imaging.

blue CRY2/CIB1 HeLa Signaling cascade control
Sci Rep, 12 Jun 2018 DOI: 10.1038/s41598-018-27174-x Link to full text
Abstract: Genetically encoded biosensors based on the principle of Förster resonance energy transfer comprise two major classes: biosensors based on fluorescence resonance energy transfer (FRET) and those based on bioluminescence energy transfer (BRET). The FRET biosensors visualize signaling-molecule activity in cells or tissues with high resolution. Meanwhile, due to the low background signal, the BRET biosensors are primarily used in drug screening. Here, we report a protocol to transform intramolecular FRET biosensors to BRET-FRET hybrid biosensors called hyBRET biosensors. The hyBRET biosensors retain all properties of the prototype FRET biosensors and also work as BRET biosensors with dynamic ranges comparable to the prototype FRET biosensors. The hyBRET biosensors are compatible with optogenetics, luminescence microplate reader assays, and non-invasive whole-body imaging of xenograft and transgenic mice. This simple protocol will expand the use of FRET biosensors and enable visualization of the multiscale dynamics of cell signaling in live animals.

Protein Phase Separation Provides Long-Term Memory of Transient Spatial Stimuli.

blue CRY2/CRY2 PixD/PixE NIH/3T3 Signaling cascade control Organelle manipulation
Cell Syst, 24 May 2018 DOI: 10.1016/j.cels.2018.05.002 Link to full text
Abstract: Protein/RNA clusters arise frequently in spatially regulated biological processes, from the asymmetric distribution of P granules and PAR proteins in developing embryos to localized receptor oligomers in migratory cells. This co-occurrence suggests that protein clusters might possess intrinsic properties that make them a useful substrate for spatial regulation. Here, we demonstrate that protein droplets show a robust form of spatial memory, maintaining the spatial pattern of an inhibitor of droplet formation long after it has been removed. Despite this persistence, droplets can be highly dynamic, continuously exchanging monomers with the diffuse phase. We investigate the principles of biophysical spatial memory in three contexts: a computational model of phase separation; a novel optogenetic system where light can drive rapid, localized dissociation of liquid-like protein droplets; and membrane-localized signal transduction from clusters of receptor tyrosine kinases. Our results suggest that the persistent polarization underlying many cellular and developmental processes could arise through a simple biophysical process, without any additional biochemical feedback loops.

Optogenetic inhibition of Gαq protein signaling reduces calcium oscillation stochasticity.

blue CRY2/CIB1 HEK293T Signaling cascade control Immediate control of second messengers
ACS Synth Biol, 24 May 2018 DOI: 10.1021/acssynbio.8b00065 Link to full text
Abstract: As fast terminators of G-protein coupled receptor (GPCR) signaling, regulators of G-protein signaling (RGS) serve critical roles in fine-tuning second messenger levels and, consequently, cellular responses to external stimuli. Here, we report the creation of an optogenetic RGS2 (opto-RGS2) that suppresses agonist-evoked calcium oscillations by the inactivation of Gαq protein. In this system, cryptochrome-mediated hetero-dimerization of the catalytic RGS2-box with its N-terminal amphipathic helix reconstitutes a functional membrane-localized complex that can dynamically suppress store-operated release of calcium. Engineered opto-RGS2 cell lines were used to establish the role of RGS2 as a key inhibitory feedback regulator of the stochasticity of the Gαq-mediated calcium spike timing. RGS2 reduced the stochasticity of carbachol-stimulated calcium oscillations, and the feedback inhibition was coupled to the global calcium elevation by calmodulin/RGS2 interactions. The identification of a critical negative feedback circuit exemplifies the utility of optogenetic approaches for interrogating RGS/GPCR biology and calcium encoding principles through temporally precise molecular gain-of-function.

Activation of EphB2 Forward Signaling Enhances Memory Consolidation.

blue CRY2olig HEK293 mouse in vivo NIH/3T3 Signaling cascade control
Cell Rep, 15 May 2018 DOI: 10.1016/j.celrep.2018.04.042 Link to full text
Abstract: EphB2 is involved in enhancing synaptic transmission and gene expression. To explore the roles of EphB2 in memory formation and enhancement, we used a photoactivatable EphB2 (optoEphB2) to activate EphB2 forward signaling in pyramidal neurons in lateral amygdala (LA). Photoactivation of optoEphB2 during fear conditioning, but not minutes afterward, enhanced long-term, but not short-term, auditory fear conditioning. Photoactivation of optoEphB2 during fear conditioning led to activation of the cAMP/Ca2+ responsive element binding (CREB) protein. Application of light to a kinase-dead optoEphB2 in LA did not lead to enhancement of long-term fear conditioning memory or to activation of CREB. Long-term, but not short-term, auditory fear conditioning memory was impaired in mice lacking EphB2 forward signaling (EphB2lacZ/lacZ). Activation of optoEphB2 in LA of EphB2lacZ/lacZ mice enhanced long-term fear conditioning memory. The present findings show that the level of EphB2 forward signaling activity during learning determines the strength of long-term memory consolidation.

Filopodia Conduct Target Selection in Cortical Neurons Using Differences in Signal Kinetics of a Single Kinase.

blue CRY2/CRY2 CRY2olig HEK293T primary mouse cortical neurons rat cortical neurons Signaling cascade control Control of cytoskeleton / cell motility / cell shape
Neuron, 30 Apr 2018 DOI: 10.1016/j.neuron.2018.04.011 Link to full text
Abstract: Dendritic filopodia select synaptic partner axons by interviewing the cell surface of potential targets, but how filopodia decipher the complex pattern of adhesive and repulsive molecular cues to find appropriate contacts is unknown. Here, we demonstrate in cortical neurons that a single cue is sufficient for dendritic filopodia to reject or select specific axonal contacts for elaboration as synaptic sites. Super-resolution and live-cell imaging reveals that EphB2 is located in the tips of filopodia and at nascent synaptic sites. Surprisingly, a genetically encoded indicator of EphB kinase activity, unbiased classification, and a photoactivatable EphB2 reveal that simple differences in the kinetics of EphB kinase signaling at the tips of filopodia mediate the choice between retraction and synaptogenesis. This may enable individual filopodia to choose targets based on differences in the activation rate of a single tyrosine kinase, greatly simplifying the process of partner selection and suggesting a general principle.

A biochemical network controlling basal myosin oscillation.

blue CRY2/CIB1 D. melanogaster in vivo Signaling cascade control Control of cytoskeleton / cell motility / cell shape
Nat Commun, 23 Mar 2018 DOI: 10.1038/s41467-018-03574-5 Link to full text
Abstract: The actomyosin cytoskeleton, a key stress-producing unit in epithelial cells, oscillates spontaneously in a wide variety of systems. Although much of the signal cascade regulating myosin activity has been characterized, the origin of such oscillatory behavior is still unclear. Here, we show that basal myosin II oscillation in Drosophila ovarian epithelium is not controlled by actomyosin cortical tension, but instead relies on a biochemical oscillator involving ROCK and myosin phosphatase. Key to this oscillation is a diffusive ROCK flow, linking junctional Rho1 to medial actomyosin cortex, and dynamically maintained by a self-activation loop reliant on ROCK kinase activity. In response to the resulting myosin II recruitment, myosin phosphatase is locally enriched and shuts off ROCK and myosin II signals. Coupling Drosophila genetics, live imaging, modeling, and optogenetics, we uncover an intrinsic biochemical oscillator at the core of myosin II regulatory network, shedding light on the spatio-temporal dynamics of force generation.

Unique Roles of β-Arrestin in GPCR Trafficking Revealed by Photoinducible Dimerizers.

blue CRY2/CIB1 HEK293 Signaling cascade control Control of vesicular transport
Sci Rep, 12 Jan 2018 DOI: 10.1038/s41598-017-19130-y Link to full text
Abstract: Intracellular trafficking of G protein-coupled receptors (GPCRs) controls their localization and degradation, which affects a cell's ability to adapt to extracellular stimuli. Although the perturbation of trafficking induces important diseases, these trafficking mechanisms are poorly understood. Herein, we demonstrate an optogenetic method using an optical dimerizer, cryptochrome (CRY) and its partner protein (CIB), to analyze the trafficking mechanisms of GPCRs and their regulatory proteins. Temporally controlling the interaction between β-arrestin and β2-adrenergic receptor (ADRB2) reveals that the duration of the β-arrestin-ADRB2 interaction determines the trafficking pathway of ADRB2. Remarkably, the phosphorylation of ADRB2 by G protein-coupled receptor kinases is unnecessary to trigger clathrin-mediated endocytosis, and β-arrestin interacting with unphosphorylated ADRB2 fails to activate mitogen-activated protein kinase (MAPK) signaling, in contrast to the ADRB2 agonist isoproterenol. Temporal control of β-arrestin-GPCR interactions will enable the investigation of the unique roles of β-arrestin and the mechanism by which it regulates β-arrestin-specific trafficking pathways of different GPCRs.

Spatiotemporal Control of TGF-β Signaling with Light.

blue CRY2/CIB1 HeLa Signaling cascade control
ACS Synth Biol, 14 Dec 2017 DOI: 10.1021/acssynbio.7b00225 Link to full text
Abstract: Cells employ signaling pathways to make decisions in response to changes in their immediate environment. Transforming growth factor beta (TGF-β) is an important growth factor that regulates many cellular functions in development and disease. Although the molecular mechanisms of TGF-β signaling have been well studied, our understanding of this pathway is limited by the lack of tools that allow the control of TGF-β signaling with high spatiotemporal resolution. Here, we developed an optogenetic system (optoTGFBRs) that enables the precise control of TGF-β signaling in time and space. Using the optoTGFBRs system, we show that TGF-β signaling can be selectively and sequentially activated in single cells through the modulation of the pattern of light stimulations. By simultaneously monitoring the subcellular localization of TGF-β receptor and Smad2 proteins, we characterized the dynamics of TGF-β signaling in response to different patterns of blue light stimulations. The spatial and temporal precision of light control will make the optoTGFBRs system as a powerful tool for quantitative analyses of TGF-β signaling at the single cell level.

Optogenetic activation of EphB2 receptor in dendrites induced actin polymerization by activating Arg kinase.

blue CRY2olig 3T3MEF Cos-7 HEK293 rat hippocampal neurons Signaling cascade control Control of cytoskeleton / cell motility / cell shape
Biol Open, 20 Nov 2017 DOI: 10.1242/bio.029900 Link to full text
Abstract: Erythropoietin-producing hepatocellular (Eph) receptors regulate a wide array of developmental processes by responding to cell-cell contacts. EphB2 is well-expressed in brain and known to be important for dendritic spine development, as well as for the maintenance of the synapses, although the mechanisms of these functions have not been fully understood. Here we studied EphB2's functions in hippocampal neurons with an optogenetic approach, which allows us to specify spatial regions of signal activation and monitor in real-time the consequences of signal activation. We designed and constructed OptoEphB2, a genetically encoded photoactivatable EphB2. Photoactivation of OptoEphB2 in fibroblast cells induced receptor phosphorylation and resulted in cell rounding - a well-known cellular response to EphB2 activation. In contrast, local activation of OptoEphb2 in dendrites of hippocampal neurons induces rapid actin polymerization, resulting dynamic dendritic filopodial growth. Inhibition of Rac1 and CDC42 did not abolish OptoEphB2-induced actin polymerization. Instead, we identified Abelson Tyrosine-Protein Kinase 2 (Abl2/Arg) as a necessary effector in OptoEphB2-induced filopodia growth in dendrites. These findings provided new mechanistic insight into EphB2's role in neural development and demonstrated the advantage of OptoEphB as a new tool for studying EphB signaling.

Design and Profiling of a Subcellular Targeted Optogenetic cAMP-Dependent Protein Kinase.

blue CRY2/CIB1 HEK293T MVD7 Signaling cascade control
Cell Chem Biol, 25 Oct 2017 DOI: 10.1016/j.chembiol.2017.09.011 Link to full text
Abstract: Although the cAMP-dependent protein kinase (PKA) is ubiquitously expressed, it is sequestered at specific subcellular locations throughout the cell, thereby resulting in compartmentalized cellular signaling that triggers site-specific behavioral phenotypes. We developed a three-step engineering strategy to construct an optogenetic PKA (optoPKA) and demonstrated that, upon illumination, optoPKA migrates to specified intracellular sites. Furthermore, we designed intracellular spatially segregated reporters of PKA activity and confirmed that optoPKA phosphorylates these reporters in a light-dependent fashion. Finally, proteomics experiments reveal that light activation of optoPKA results in the phosphorylation of known endogenous PKA substrates as well as potential novel substrates.

Efficient synthesis of phycocyanobilin in mammalian cells for optogenetic control of cell signaling.

red PhyB/PIF3 PhyB/PIF6 HEK293T HeLa mESCs Signaling cascade control
Proc Natl Acad Sci USA, 24 Oct 2017 DOI: 10.1073/pnas.1707190114 Link to full text
Abstract: Optogenetics is a powerful tool to precisely manipulate cell signaling in space and time. For example, protein activity can be regulated by several light-induced dimerization (LID) systems. Among them, the phytochrome B (PhyB)-phytochrome-interacting factor (PIF) system is the only available LID system controlled by red and far-red lights. However, the PhyB-PIF system requires phycocyanobilin (PCB) or phytochromobilin as a chromophore, which must be artificially added to mammalian cells. Here, we report an expression vector that coexpresses HO1 and PcyA with Ferredoxin and Ferredoxin-NADP+ reductase for the efficient synthesis of PCB in the mitochondria of mammalian cells. An even higher intracellular PCB concentration was achieved by the depletion of biliverdin reductase A, which degrades PCB. The PCB synthesis and PhyB-PIF systems allowed us to optogenetically regulate intracellular signaling without any external supply of chromophores. Thus, we have provided a practical method for developing a fully genetically encoded PhyB-PIF system, which paves the way for its application to a living animal.

Optogenetic control of focal adhesion kinase signaling.

blue CRY2/CRY2 HEK293 HEK293T HeLa Signaling cascade control
Cell Signal, 23 Oct 2017 DOI: 10.1016/j.cellsig.2017.10.012 Link to full text
Abstract: Focal adhesion kinase (FAK) integrates signaling from integrins, growth factor receptors and mechanical stress to control cell adhesion, motility, survival and proliferation. Here, we developed a single-component, photo-activatable FAK, termed optoFAK, by using blue light-induced oligomerization of cryptochrome 2 (CRY2) to activate FAK-CRY2 fusion proteins. OptoFAK functions uncoupled from physiological stimuli and activates downstream signaling rapidly and reversibly upon blue light exposure. OptoFAK stimulates SRC creating a positive feedback loop on FAK activation, facilitating phosphorylation of paxillin and p130Cas in adherent cells. In detached cells or in mechanically stressed adherent cells, optoFAK is autophosphorylated upon exposure to blue light, however, downstream signaling is hampered indicating that the accessibility to these substrates is disturbed. OptoFAK may prove to be a useful tool to study the biological function of FAK in growth factor and integrin signaling, tension-mediated focal adhesion maturation or anoikis and could additionally serve as test system for kinase inhibitors.

Understanding CRY2 interactions for optical control of intracellular signaling.

blue CRY2/CIB1 CRY2/CRY2 CRY2olig Cos-7 HEK293T Signaling cascade control
Nat Commun, 15 Sep 2017 DOI: 10.1038/s41467-017-00648-8 Link to full text
Abstract: Arabidopsis cryptochrome 2 (CRY2) can simultaneously undergo light-dependent CRY2-CRY2 homo-oligomerization and CRY2-CIB1 hetero-dimerization, both of which have been widely used to optically control intracellular processes. Applications using CRY2-CIB1 interaction desire minimal CRY2 homo-oligomerization to avoid unintended complications, while those utilizing CRY2-CRY2 interaction prefer robust homo-oligomerization. However, selecting the type of CRY2 interaction has not been possible as the molecular mechanisms underlying CRY2 interactions are unknown. Here we report CRY2-CIB1 and CRY2-CRY2 interactions are governed by well-separated protein interfaces at the two termini of CRY2. N-terminal charges are critical for CRY2-CIB1 interaction. Moreover, two C-terminal charges impact CRY2 homo-oligomerization, with positive charges facilitating oligomerization and negative charges inhibiting it. By engineering C-terminal charges, we develop CRY2high and CRY2low with elevated or suppressed oligomerization respectively, which we use to tune the levels of Raf/MEK/ERK signaling. These results contribute to our understanding of the mechanisms underlying light-induced CRY2 interactions and enhance the controllability of CRY2-based optogenetic systems.Cryptochrome 2 (CRY2) can form light-regulated CRY2-CRY2 homo-oligomers or CRY2-CIB1 hetero-dimers, but modulating these interactions is difficult owing to the lack of interaction mechanism. Here the authors identify the interactions facilitating homo-oligomers and introduce mutations to create low and high oligomerization versions.
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